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<div class="section" id="push-front">
<h1><a class="toc-backref" href="./intrinsic-metafunctions.html#id1444">push_front</a></h1>
<div class="section" id="id345">
<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
<pre class="literal-block">
template&lt;
      typename Sequence
    , typename T
    &gt;
struct <a href="./push-front.html" class="identifier">push_front</a>
{
    typedef <em>unspecified</em> type;
};
</pre>
</div>
<div class="section" id="id346">
<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
<p><tt class="literal"><span class="pre"><a href="./push-front.html" class="identifier">push_front</a></span></tt> performs an insertion at the beginning of the sequence with guaranteed <em>O(1)</em>
complexity.</p>
</div>
<div class="section" id="id347">
<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
<pre class="literal-block">
#include &lt;<a href="../../../../boost/mpl/push_front.hpp" class="header">boost/mpl/push_front.hpp</a>&gt;
</pre>
</div>
<div class="section" id="id348">
<h3><a class="subsection-title" href="#model-of" name="model-of">Model of</a></h3>
<p><a class="reference internal" href="./tag-dispatched-metafunction.html">Tag Dispatched Metafunction</a></p>
</div>
<div class="section" id="id349">
<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
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<col width="33%" />
<col width="51%" />
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<tr><th class="head">Parameter</th>
<th class="head">Requirement</th>
<th class="head">Description</th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="literal"><span class="pre">Sequence</span></tt></td>
<td><a class="reference internal" href="./front-extensible-sequence.html">Front Extensible Sequence</a></td>
<td>A sequence to insert into.</td>
</tr>
<tr><td><tt class="literal"><span class="pre">T</span></tt></td>
<td>Any type</td>
<td>The element to be inserted.</td>
</tr>
</tbody>
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<div class="section" id="id350">
<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
<p>For any <a class="reference internal" href="./front-extensible-sequence.html">Front Extensible Sequence</a> <tt class="literal"><span class="pre">s</span></tt> and arbitrary type <tt class="literal"><span class="pre">x</span></tt>:</p>
<pre class="literal-block">
typedef <a href="./push-front.html" class="identifier">push_front</a>&lt;s,x&gt;::type r;
</pre>
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<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./front-extensible-sequence.html">Front Extensible Sequence</a>.</p>
</td>
</tr>
<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p>
<pre class="literal-block">
typedef <a href="./insert.html" class="identifier">insert</a>&lt; s,<a href="./begin.html" class="identifier">begin</a>&lt;s&gt;::type,x &gt;::type r;
</pre>
</td>
</tr>
<tr class="field"><th class="field-name">Postcondition:</th><td class="field-body"><p class="first last"><tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a>&lt;r&gt;::value</span> <span class="pre">==</span> <span class="pre"><a href="./size.html" class="identifier">size</a>&lt;s&gt;::value</span> <span class="pre">+</span> <span class="pre">1</span></tt>;
<tt class="literal"><span class="pre"><a href="./front.html" class="identifier">front</a>&lt;r&gt;::type</span></tt> is identical to <tt class="literal"><span class="pre">x</span></tt>.</p>
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<div class="section" id="id351">
<h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
<p>Amortized constant time.</p>
</div>
<div class="section" id="id352">
<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
<pre class="literal-block">
typedef <a href="./vector-c.html" class="identifier">vector_c</a>&lt;int,1,2,3,5,8,13,21&gt; v;
<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./size.html" class="identifier">size</a>&lt;v&gt;::value, ==, 7 );

typedef <a href="./push-front.html" class="identifier">push_front</a>&lt; v,<a href="./integral-c.html" class="identifier">integral_c</a>&lt;int,1&gt; &gt;::type fibonacci;
<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./size.html" class="identifier">size</a>&lt;fibonacci&gt;::value, ==, 8 );

<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./equal.html" class="identifier">equal</a>&lt;
      fibonacci
    , <a href="./vector-c.html" class="identifier">vector_c</a>&lt;int,1,1,2,3,5,8,13,21&gt;
    , <a href="./equal-to.html" class="identifier">equal_to</a>&lt;_,_&gt;
    > ));
</pre>
</div>
<div class="section" id="id353">
<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
<p><a class="reference internal" href="./front-extensible-sequence.html">Front Extensible Sequence</a>, <a class="reference internal" href="./insert.html">insert</a>, <a class="reference internal" href="./pop-front.html">pop_front</a>, <a class="reference internal" href="./front.html">front</a>, <a class="reference internal" href="./push-back.html">push_back</a></p>
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